Abstract: Comparative studies were performed to analyze the mechanical properties, flexural failure modes, distribution of the load-displacement and cross sectional stress of the mid-span as well as the changes of the shear stress-strain of the composite beams. A total of eight (8) U-section thin-walled steel-concrete composite beams were tested for the shear resistance behavior. The results indicates that, compared with the steel beams and the other concretesteel composite beams, a better ductility can be found in the U-section thin-walled steel-concrete composite beams under the shear failure mode. Since it is filled with the concrete in the web, the beam web's buckling mode changes from the three half-buckling wave to one half-buckling wave, the load carrying capacity of the composite bean was improved significantly compared with the steel beam. The flexural failure of the U-section thin-walled steel-concrete composite beam occurred when the shear span ratio is less than 2. At the flexure failure, the shear span ratio of U-section composite beam is less than that of the conventional steel-concrete composite beam.

Key words: U-section Thin-walled Steel-Concrete Composite Beam, Shear Behavior, Failure Modes, Experimental Studies